/*
 * MD5C.C - RSA Data Security, Inc., MD5 message-digest algorithm
 */

/*
 * Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All rights
 * reserved.
 * 
 * License to copy and use this software is granted provided that it is
 * identified as the "RSA Data Security, Inc. MD5 Message-Digest Algorithm"
 * in all material mentioning or referencing this software or this function.
 * 
 * License is also granted to make and use derivative works provided that such
 * works are identified as "derived from the RSA Data Security, Inc. MD5
 * Message-Digest Algorithm" in all material mentioning or referencing the
 * derived work.
 * 
 * RSA Data Security, Inc. makes no representations concerning either the
 * merchantability of this software or the suitability of this software for
 * any particular purpose. It is provided "as is" without express or implied
 * warranty of any kind.
 * 
 * These notices must be retained in any copies of any part of this
 * documentation and/or software.
 */

#include "md5.h"

#include <string.h>

/*
 * Constants for MD5Transform routine.
 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static void MD5Transform (UINT4[4], unsigned char[64]);
static void Encode (unsigned char *, UINT4 *, unsigned int);
static void Decode (UINT4 *, unsigned char *, unsigned int);

static unsigned char PADDING[64] = {
        0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/*
 * F, G, H and I are basic MD5 functions.
 */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/*
 * ROTATE_LEFT rotates x left n bits.
 */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/*
 * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4. Rotation is
 * separate from addition to prevent recomputation.
 */
#define FF(a, b, c, d, x, s, ac) { \
 (a) += F ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

/*
 * MD5 initialization. Begins an MD5 operation, writing a new context.
 */
void 
MD5Init( MD5_CTX        *context)/* context */
{
        context->count[0] = context->count[1] = 0;
        /*
         * Load magic initialization constants.
         */
        context->state[0] = 0x67452301;
        context->state[1] = 0xefcdab89;
        context->state[2] = 0x98badcfe;
        context->state[3] = 0x10325476;
}

/*
 * MD5 block update operation. Continues an MD5 message-digest operation,
 * processing another message block, and updating the context.
 */
void 
MD5Update(
        MD5_CTX        *context,/* context */
        unsigned char  *input,  /* input block */
        unsigned int    inputLen)       /* length of input block */
{
        unsigned int    i, index, partLen;

        /* Compute number of bytes mod 64 */
        index = (unsigned int) ((context->count[0] >> 3) & 0x3F);

        /* Update number of bits */
        if ((context->count[0] += ((UINT4) inputLen << 3))
            < ((UINT4) inputLen << 3))
                context->count[1]++;
        context->count[1] += ((UINT4) inputLen >> 29);

        partLen = 64 - index;

        /*
         * Transform as many times as possible.
         */
        if (inputLen >= partLen) {
                memcpy
                        ((POINTER) & context->buffer[index], (POINTER) input, partLen);
                MD5Transform(context->state, context->buffer);

                for (i = partLen; i + 63 < inputLen; i += 64)
                        MD5Transform(context->state, &input[i]);

                index = 0;
        } else
                i = 0;

        /* Buffer remaining input */
        memcpy
                ((POINTER) & context->buffer[index], (POINTER) & input[i],
                 inputLen - i);
}

/*
 * MD5 finalization. Ends an MD5 message-digest operation, writing the the
 * message digest and zeroizing the context.
 */
void 
MD5Final(
        unsigned char   digest[16],     /* message digest */
        MD5_CTX        *context)  /* context */
{
        unsigned char   bits[8];
        unsigned int    index, padLen;

        /* Save number of bits */
        Encode(bits, context->count, 8);

        /*
         * Pad out to 56 mod 64.
         */
        index = (unsigned int) ((context->count[0] >> 3) & 0x3f);
        padLen = (index < 56) ? (56 - index) : (120 - index);
        MD5Update(context, PADDING, padLen);

        /* Append length (before padding) */
        MD5Update(context, bits, 8);

        /* Store state in digest */
        Encode(digest, context->state, 16);

        /*
         * Zeroize sensitive information.
         */
        memset((POINTER) context, 0, sizeof(*context));
}

/*
 * MD5 basic transformation. Transforms state based on block.
 */
static void 
MD5Transform(
        UINT4           state[4],
        unsigned char   block[64])
{
        UINT4           a = state[0], b = state[1], c = state[2], d = state[3],
                        x[16];

        Decode(x, block, 64);

        /* Round 1 */
        FF(a, b, c, d, x[0], S11, 0xd76aa478);  /* 1 */
        FF(d, a, b, c, x[1], S12, 0xe8c7b756);  /* 2 */
        FF(c, d, a, b, x[2], S13, 0x242070db);  /* 3 */
        FF(b, c, d, a, x[3], S14, 0xc1bdceee);  /* 4 */
        FF(a, b, c, d, x[4], S11, 0xf57c0faf);  /* 5 */
        FF(d, a, b, c, x[5], S12, 0x4787c62a);  /* 6 */
        FF(c, d, a, b, x[6], S13, 0xa8304613);  /* 7 */
        FF(b, c, d, a, x[7], S14, 0xfd469501);  /* 8 */
        FF(a, b, c, d, x[8], S11, 0x698098d8);  /* 9 */
        FF(d, a, b, c, x[9], S12, 0x8b44f7af);  /* 10 */
        FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
        FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
        FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
        FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
        FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
        FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

        /* Round 2 */
        GG(a, b, c, d, x[1], S21, 0xf61e2562);  /* 17 */
        GG(d, a, b, c, x[6], S22, 0xc040b340);  /* 18 */
        GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
        GG(b, c, d, a, x[0], S24, 0xe9b6c7aa);  /* 20 */
        GG(a, b, c, d, x[5], S21, 0xd62f105d);  /* 21 */
        GG(d, a, b, c, x[10], S22, 0x2441453);  /* 22 */
        GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
        GG(b, c, d, a, x[4], S24, 0xe7d3fbc8);  /* 24 */
        GG(a, b, c, d, x[9], S21, 0x21e1cde6);  /* 25 */
        GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
        GG(c, d, a, b, x[3], S23, 0xf4d50d87);  /* 27 */
        GG(b, c, d, a, x[8], S24, 0x455a14ed);  /* 28 */
        GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
        GG(d, a, b, c, x[2], S22, 0xfcefa3f8);  /* 30 */
        GG(c, d, a, b, x[7], S23, 0x676f02d9);  /* 31 */
        GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

        /* Round 3 */
        HH(a, b, c, d, x[5], S31, 0xfffa3942);  /* 33 */
        HH(d, a, b, c, x[8], S32, 0x8771f681);  /* 34 */
        HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
        HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
        HH(a, b, c, d, x[1], S31, 0xa4beea44);  /* 37 */
        HH(d, a, b, c, x[4], S32, 0x4bdecfa9);  /* 38 */
        HH(c, d, a, b, x[7], S33, 0xf6bb4b60);  /* 39 */
        HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
        HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
        HH(d, a, b, c, x[0], S32, 0xeaa127fa);  /* 42 */
        HH(c, d, a, b, x[3], S33, 0xd4ef3085);  /* 43 */
        HH(b, c, d, a, x[6], S34, 0x4881d05);   /* 44 */
        HH(a, b, c, d, x[9], S31, 0xd9d4d039);  /* 45 */
        HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
        HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
        HH(b, c, d, a, x[2], S34, 0xc4ac5665);  /* 48 */

        /* Round 4 */
        II(a, b, c, d, x[0], S41, 0xf4292244);  /* 49 */
        II(d, a, b, c, x[7], S42, 0x432aff97);  /* 50 */
        II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
        II(b, c, d, a, x[5], S44, 0xfc93a039);  /* 52 */
        II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
        II(d, a, b, c, x[3], S42, 0x8f0ccc92);  /* 54 */
        II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
        II(b, c, d, a, x[1], S44, 0x85845dd1);  /* 56 */
        II(a, b, c, d, x[8], S41, 0x6fa87e4f);  /* 57 */
        II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
        II(c, d, a, b, x[6], S43, 0xa3014314);  /* 59 */
        II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
        II(a, b, c, d, x[4], S41, 0xf7537e82);  /* 61 */
        II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
        II(c, d, a, b, x[2], S43, 0x2ad7d2bb);  /* 63 */
        II(b, c, d, a, x[9], S44, 0xeb86d391);  /* 64 */

        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;

        /*
         * Zeroize sensitive information.
         */
        memset((POINTER) x, 0, sizeof(x));
}

/*
 * Encodes input (UINT4) into output (unsigned char). Assumes len is a
 * multiple of 4.
 */
static void 
Encode( unsigned char  *output,
        UINT4          *input,
        unsigned int    len)
{
        unsigned int    i, j;

        for (i = 0, j = 0; j < len; i++, j += 4) {
                output[j] = (unsigned char) (input[i] & 0xff);
                output[j + 1] = (unsigned char) ((input[i] >> 8) & 0xff);
                output[j + 2] = (unsigned char) ((input[i] >> 16) & 0xff);
                output[j + 3] = (unsigned char) ((input[i] >> 24) & 0xff);
        }
}

/*
 * Decodes input (unsigned char) into output (UINT4). Assumes len is a
 * multiple of 4.
 */
static void 
Decode( UINT4          *output,
        unsigned char  *input,
        unsigned int    len)
{
        unsigned int    i, j;

        for (i = 0, j = 0; j < len; i++, j += 4)
                output[i] = ((UINT4) input[j]) | (((UINT4) input[j + 1]) << 8) |
                        (((UINT4) input[j + 2]) << 16) | (((UINT4) input[j + 3]) << 24);
}

